1. Field of the Invention
The present invention relates to an electronic device and a method of applying a voltage to a capacitor.
2. Description of the Related Art
ABO3 perovskite type dielectric materials such as BST ((Ba,Sr)TiO3), and the like are currently being investigated widely as applications for the capacitor dielectric film in the decoupling capacitor, DRAM (Dynamic Random Access Memory), and so on. Also, ABO3 perovskite type dielectric materials with the ferroelectric characteristic are currently being investigated as the capacitor dielectric film in the nonvolatile memories such as FeRAM (Ferroelectric Random Access Memory), and so on.
DC voltage is usually applied to the dielectric film, which is used in such element, for a considerable long time in practical use.
Technologies relevant to the present invention are disclosed in Patent Literatures 1, 2.                [Patent Literature 1] Patent Application Publication (KOKAI) Hei 10-93050        [Patent Literature 2] Patent Application Publication (KOKAI) 2004-88892        
When the capacitor dielectric film is exposed to the electric field for a long time in this manner, such a problem is caused that the reliability of the capacitor is lowered. It is known that, when the capacitor dielectric film made of high-dielectric material or ferroelectric material is subjected to an electrical stress, the film is degraded due to movement of electrons or ions in the film. As the mechanism of such degradation, resistance degradation, TDDB (Time Dependent Dielectric Breakdown), etc. have been reported.
If the capacitor dielectric film is degraded in this manner, a leakage current exceeding an allowable value is generated between the top electrode and the bottom electrode constituting the capacitor and then the lifetime of the capacitor is shortened. Therefore, an electronic device that is capable of enhancing the lifetime of the capacitor by preventing degradation of the capacitor dielectric film is required.